Just bought a new bike and it is a .giant liv Mtb for my wife it is 2×10 . When the gears are. In the smaller cog on the front and the bigger cogs on the back , the chain is rubbing on the inside of the mech, the tension is too much on the cable as the mech is not hitting the low screw but if I reduce the tension it won’t changes up onto the bigger front cog, please help cheers

Take it back to the shop to set it up properly if you’re not confident doing it yourself.

They should do it for free as it is a new bike.

^

this – or if for some reason you can’t (mail order?) then it’s not that hard but you’re better starting from scratch imho than trying to adjust something that’s not right in the first place. Park Tools website is a good resource, or google the part number on the shimano website for the official leaflet.

Not sure if that bike is shinano or sram equipped – but if you google pink bike derailleur setup they gave a great video instruction guide which I’ve used a few times.